4
INSTALLATION CONSIDERATIONS
Models
There are four models in the Legacy Series: programmable and non--programmable, AC
and HP. Models T2--PAC and T2--NAC are designed for AC systems, controlling one
stage of cooling and one stage of heating. They will not operate a heat pump. Models
T2--PHP and T2--NHP are designed for HP systems, controlling two stages of cooling
and three stages of heating. They can be converted to AC operation. Select the
appropriate model for the intended application.
Power
All Legacy Series models are dual powered. They can operate from batteries or
24VAC power. Operation from 24VAC is preferred if available. Battery operation is
used when there are not enough wires to support 24VAC operation or when
“armchair programming” is desired. For an AC system, up to six wires are needed
for 24VAC operation and one less wire for battery operation. For a HP system, up to
seven wires are needed for 24VAC operation and and one less wire is sufficient for
battery operation. For heat only operation with batteries, only two wires are
required. When battery operation is used, the C terminal does not need to be
connected.
Provision is also made for separate heating and cooling transformers via separable Rc
and Rh terminals which are connected via factory--installed jumper wire.
